How do you diagnose dementia and assess its severity?

Diagnosing Dementia and Assessing Its Severity

Dementia diagnosis requires a multi-dimensional assessment approach that combines patient history, cognitive testing, functional evaluation, and informant reports, with diagnosis based on cognitive or behavioral symptoms that interfere with daily functioning, represent a decline from previous levels, and are not explained by delirium or psychiatric disorders. 1

Core Diagnostic Criteria for Dementia

• Dementia is diagnosed when cognitive or behavioral symptoms:

  • Interfere with ability to function at work or usual activities 1
  • Represent a decline from previous functioning 1
  • Are not explained by delirium or major psychiatric disorder 1
  • Are detected through history-taking and objective cognitive assessment 1

• Key cognitive domains to assess include:

  • Memory (impaired ability to acquire and remember new information) 1
  • Executive function (impaired reasoning, judgment, and handling of complex tasks) 1
  • Visuospatial abilities (inability to recognize faces or objects despite good acuity) 1
  • Language functions (difficulty with speaking, reading, writing) 1
  • Personality and behavior changes (mood fluctuations, apathy, social withdrawal) 1

Diagnostic Assessment Tools

Cognitive Screening Tests

• Initial cognitive screening tools:

  • Mini-Mental State Examination (MMSE) - widely used with high sensitivity and specificity for moderate dementia 1, 2
  • Montreal Cognitive Assessment (MoCA) - more sensitive for mild cognitive impairment and early dementia 1, 2
  • Mini-Cog test - comparable performance to MMSE with good sensitivity (0.91) and specificity (0.86) 2
  • Clock Drawing Test - useful supplementary test 1

• For atypical presentations:

  • Dementia Cognitive Questionnaire (DCQ) - specifically developed for atypical syndromes like frontotemporal dementia 1
  • Addenbrooke's Cognitive Examination-Revised (ACE-R) - high sensitivity (0.92) and specificity (0.89) 2

• Important caveat: Diagnosis should not be solely based on impaired cognitive screening test results 1

Functional Assessment

• Evaluate impact on Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs) using:
  • Disability Assessment in Dementia (DAD) 1
  • Functional Activities Questionnaire (FAQ) 1
  • Lawton Instrumental Activities of Daily Living Scale 1
  • Functional Assessment Staging Scale (FAST) 1

Behavioral Assessment

• Evaluate behavioral and psychological symptoms using:
  • Neuropsychiatric Inventory-Questionnaire (NPI-Q) - brief version for clinical practice 1
  • Geriatric Depression Scale (GDS) or Patient Health Questionnaire (PHQ-9) 1
  • Mild Behavioral Impairment Checklist (MBI-C) 1

Informant Reports

• Obtaining corroborative history is essential and has prognostic significance 1
• Recommended informant-based tools:
  • Everyday Cognition (ECog) - for cognitive changes 1
  • Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) - for cognitive and functional changes 1
  • Quick Dementia Rating System (QDRS) - for cognitive and functional changes 1

Diagnostic Workup

Laboratory Testing

• Standard dementia medical workup should include:
  • Thyroid-stimulating hormone (TSH) 3, 4
  • Vitamin B12 levels 3, 4
  • Other tests guided by history and physical examination 4

Neuroimaging

• Anatomical neuroimaging is recommended in most situations, especially with:

  • Onset of cognitive symptoms within past 2 years 1
  • Unexpected decline in cognition/function 1
  • Recent significant head trauma 1
  • Unexplained neurological manifestations 1
  • Significant vascular risk factors 1

• MRI is preferred over CT, especially for detecting vascular lesions 1

  • Recommended sequences: 3D T1 volumetric, FLAIR, T2, and diffusion-weighted imaging 1

Assessing Severity of Dementia

• Severity assessment should be based on:

  • Degree of cognitive impairment (using standardized tests like MMSE or MoCA) 1
  • Level of functional impairment in daily activities 1
  • Presence and severity of behavioral symptoms 1

• For longitudinal tracking:

  • MMSE is recommended as a primary tool for tracking cognitive changes over time 1
  • Assessment should occur every 6-12 months, with more frequent assessment for patients with behavioral symptoms 1
  • Use longitudinal serial cognitive assessments (like QuoCo curves) to optimize accuracy 1

Special Considerations

Subjective Cognitive Decline (SCD)

• For patients with cognitive concerns but normal testing:
  • Conduct appropriate diagnostic workup to identify reversible causes 1
  • Obtain reliable informant information about changes in cognition, function, and behavior 1
  • Use structured scales for objective and subjective cognition 1
  • For negative corroborative history: provide reassurance and follow-up as needed 1
  • For positive corroborative history: schedule annual follow-ups 1

Mild Cognitive Impairment (MCI)

• Differentiation from dementia rests on whether there is significant interference with daily functioning 1
• Montreal Cognitive Assessment (MoCA) has the best performance for detecting MCI with 0.89 sensitivity and 0.75 specificity 2

Tracking Response to Treatment and Disease Progression

• Use a multi-dimensional approach that includes assessment of:

  • Cognition (using MMSE, MoCA, or other validated tools) 1
  • Functional autonomy (using DAD, FAQ, or other functional scales) 1
  • Behavioral symptoms (using NPI-Q or other behavioral scales) 1
  • Caregiver burden (using Zarit Burden Interview) 1

• All domains must be evaluated at least annually, with more frequent assessment for patients with behavioral symptoms 1